In a bowl, combine the bread crumbs, cheese, leek, walnuts, sage, lemon zest, and mustard powder.,Gradually blend the goat cheese into the mixture.,Separate 1 egg, reserving the white and adding the yolk to the remaining egg.,Beat the egg and yolk into the cheese mixture with the milk.,Season to taste.,Divide the mixture into 8 pieces and roll into sausages about 3 inches long.,Cover and chill for about 1 hour to allow the flavors to develop.,Sprinkle the flour onto a plate.,Brush the sausages with the reserved egg white, then dip into the flour until lightly coated all over.,______,Heat the oil in a skillet, add the sausages, and cook over medium heat,turning occasionally, for 8-10 minutes, until golden.,Drain on paper towels, and serve immediately, garnished with sage.,Enjoy!